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There was I, diggin' this hole...


ToughButterCup

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and just like Bernard Cribbins, I'm left wondering how deep it should be?

 

The job? Connect the outfall from the digester to the stream 100 meters away. Across a field that -in season- has cattle on it sometimes.

I asked the farmer how deep he wanted it. He had no idea. I've looked at the Regs, and there appears to be no clear guidance.

 

So, I'm asking you for advice, please.

I'm thinking about the bloke in the bowler who might come along and scratch his head (0:28)

 

 

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How deep will depend on how high the outfeed from your digester sits and how much fall you need to get to the steam. Min of 1m I would reckon so the farmer can more or less do whatever he wants with the field with no risk of hitting your pipe.

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http://www.ldca.org/LDCA Technical Specification for Field Drainage Schemes 2014.pdf

 

3.2.4

 

min 600mm cover

 

but as above this will depend if you need to create a fall or just run with the land

 

also you may want to ask the farmer if there are any existing land drains across the meadow to avoid any issues

Edited by Construction Channel
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16 minutes ago, Construction Channel said:

http://www.ldca.org/LDCA Technical Specification for Field Drainage Schemes 2014.pdf

 

3.2.4

 

min 600mm cover

 

but as above this will depend if you need to create a fall or just run with the land

 

also you may want to ask the farmer if there are any existing land drains across the meadow to avoid any issues

 

Hmm me thinks that link needs pinning ..!

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2 hours ago, recoveringacademic said:

The job? Connect the outfall from the digester to the stream 100 meters away.

 

I remember seeing guidance for stream end (the outfall into the stream). That might set the height that end. Will try and find it.

 

Then working back up from there to the digester you need a fall on the pipe. At 1:40 that would be 2.5 meters over 100m.

 

 

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It won't matter on slope for the outfall as it's a digester output so is clean water - 1:200 will be fine as long as the bottom end is above the flood level of the stream. Maybe put a NRV or rat flap on the end for good measure. 

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Thought I had seen dimensions on the Paving Expert site but I was mistaken. That just refers to..

 

http://www.pavingexpert.com/drain03.htm

 

"Most local authorities and/or water boards have their own specification for an outfall detail, but the illustration opposite shows the type of scheme favoured by many authorities for small outfalls."

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as i have thought more about this, assuming you are not crossing any existing land drains you would probably be best to make the bottom of your trench about 900mm, 

this would leave the top of your 4" pipe (assumption) about 800 down so this would still allow a 6" land drain to cross above it and still get the 600 cover, ya get me??

 

also map the run accurately and give a copy to the land owner for future reference. :) 

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OK lads, thanks.

Here's my Method Statement (RAMS) . I'm using Ed's reference:  LDCA Technical Specification for Field Drainage, and H1 of the Building Regs (as applicable)

 

The job is to lay a pipe across an open field. The pipe takes the discharge for two properties from the digester (sited more than 10 meters away from a water course and other buildings) . That means the discharge water is classified as clean. I think the worst case scenario will be when the farmer decides he wants to deep-plough the field.

  • The land drains which already exist (2) have been surveyed and checked: both of those run in exact parallel, and the pipe I'm laying runs in parallel with them,  so there's no fear my work of cutting them. Both of those drains appear to be buried deeper than 1 meter.
  • There is no track in the field.
  • There are no underground services.
  • Our pipe  run will be in a dead straight line.
  • I'll use a corrugated plastic pipe.
  • There is at least 5 meters fall over  100 meters run, so I can '...run with the land...' (above) 
  • The farmer has  assured me that no stock is due to be put on the field this year.
  • The hedge will be dug out and temporary fencing installed pending reinstatement.

 

Access and egress to the work will be through the hedge. The fall to the field to be made up with  the spoil from the digester hole and other locally dug materials. That material to be removed at the end of the job. 

 

The trench will be dug by machine. 

 

The farmer and land owner will be given an accurate sketch map of the pipe position and depth.

 

Ed, ( @Construction Channel) what's the maximum depth that ''deep ploughing' might reach? Wikipedia has it at 50cm.... Do you agree? I recon the risk of that happening is small, though.

 

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its not so much the ploughing that you need to worry about. 500mm sounds a very deep plough to me, unless it was a single furrow it would take a hell of a machine to pull it, 

 

mole drainers are about the deepest things that will be used. especially as you're running parallel to the existing land drain,  moles will run perpendicular above the land drains but usually about 500mm ;) 

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Errr.... the Proforge one my lad used to use will go to 750mm when pulled by something with 200+HP...!

 

as Ed says though - that is the exception ..! If it's all down hill and you're using plastic can the farmer not mole it in for you ..?

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9 minutes ago, PeterW said:

the Proforge one my lad used to use will go to 750mm when pulled by something with 200+HP...!

 i assume you mean a mole? otherwise that is a very big plough :o 

 

they can mole deeper if it is very fast draining land, but the mole only needs to hit the stone above the land drain and stay below a subsoiler. so it will usually stay as shallow as possible so it is easier to pull. 

 

 

 

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